1. Field of the Invention
The present invention relates to an ultrasonic endoscope whose insertion portion includes a distal hard portion which has an endoscopic observation unit having an observation field of view forwardly of the endoscopic observation unit, and an electronic scanning type of an ultrasonic observation unit having a circular or arcuate ultrasonic scanning plane perpendicular to the axis of the distal hard portion.
2. Description of the Related Art
A so-called electronic scanning type of ultrasonic endoscope has heretofore been widely used in which endoscopic observation means for observing a body cavity, an endoscopic mechanism including other means such as a treatment equipment insertion path through which to insert forceps or other treatment equipments, and ultrasonic observation means are fitted in a distal hard portion of an insertion portion and the ultrasonic observation means performs scanning by sequentially driving a multiplicity of ultrasonic transducers arranged in a predetermined direction in the ultrasonic observation means. For example, JP-A-2001-314403 describes a direct-view endoscope which has a field of view forwardly of a distal hard portion of its insertion portion as an observation field of view in the endoscopic observation means and in which the ultrasonic observation means has an ultrasonic scanning plane in its radial direction, i.e., a circular ultrasonic scanning plane or an ultrasonic scanning plane which is arcuate in a predetermined angular range.
The ultrasonic endoscope described in JP-A-2001-314403 is inserted into a body cavity tube, for example, an upper gastrointestinal tract such as the esophagus or the small intestine, or a lower gastrointestinal tract such as the large intestine, and an area which appears forward in the insertion direction is observed by the endoscopic observation means. If an area of interest such as an lesion is detected, the ultrasonic observation means is positioned to face the area of interest so that information about body tissues in the area can be acquired.
In the ultrasonic endoscope having the construction described in JP-A-2001-314403, members constituting the endoscopic observation means, at least an illumination section and an observation section, a treatment equipment insertion channel through which treatment equipments such as forceps are to be inserted, and other members such as an air/water supply tube for cleaning the observation section are arranged so as to face the distal end surface of the distal hard portion. Since the ultrasonic observation means performs radial ultrasonic scanning, the ultrasonic observation means has an approximately cylindrical shape and a tunnel-shaped path is formed in the inside of a section in which the ultrasonic observation means is fitted, and the members constituting the endoscopic observation means are arranged in the inside of the tunnel-shaped path.
The ultrasonic observation means which performs radial ultrasonic electronic canning has a multiplicity of ultrasonic transducers arranged in a cylindrical or arcuate form, and at least an acoustic lens, more strictly, an acoustic matching layer and an acoustic lens are provided on a transmission/reception surface side, i.e., an outer circumferential side, of the ultrasonic transducers. Backing materials are arranged on a surface opposite to the transmission/reception surface of the ultrasonic transducers. Accordingly, the inner circumferential surface of the backing material forms the inside diameter of the tunnel-shaped path. All the members constituting the endoscopic observation means must be arranged in a predetermined arrangement relationship so that all the members are housed in the tunnel-shaped path.
The thickness dimension of each of the ultrasonic transducers constituting the endoscopic observation means, and the thickness dimension of the acoustic lens as well as the thickness dimension of the backing material are respectively set in functional terms. The size of each of the members constituting the endoscopic observation means, for example, the sizes of an illumination lens and a light guide which constitute an illumination section, the size of an objective lens constituting the observation section, the size of a lens barrel for the objective lens, the size of a solid-state image pickup device, the size of a circuit board for the solid-state image pickup device, and the cross-sectional size of the treatment equipment insertion channel must be those necessary to realize their functions. Accordingly, if the sizes of the respective members constituting the ultrasonic observation means and the endoscopic observation means are made equivalent to dimensions necessary for their respective functions, the outside diameter of the distal hard portion increases and the operationality with which the distal hard portion is to be inserted into a body cavity is not only degraded, but also a large burden is imposed on a subject. On the other hand, if the outside diameter of the distal hard portion is to be reduced, any one or a plurality of members constituting the ultrasonic observation means or the endoscopic observation means must be reduced in size, so that functional restrictions arise.
The invention has been made in view of the above-mentioned problems, and an object of the invention is to make it possible to minimize the outside diameter of the distal hard portion in the insertion portion without reducing to an unnecessary extent the size of each of members constituting the ultrasonic observation means and the endoscopic observation means.
An ultrasonic transducer array is generally made of an approximately cylindrical unit, and a backing layer is arranged in the inside of ultrasonic transducers, while an acoustic lens is fitted on the outside of the ultrasonic transducers. The acoustic lens serves to focus ultrasonic beams transmitted from the ultrasonic transducers, and beams in directions perpendicular to an ultrasonic-wave transmission plane are improved by the acoustic lens. The ultrasonic transducer array is integrated with the above-mentioned members and the like and is incorporated in the distal hard portion of the insertion portion, and each member constituting the endoscopic observation means and the like is inserted through the inside of the ultrasonic transducer array formed in a cylindrical shape in this manner, specifically, a tunnel-shaped path formed in the inside of the backing layer.
According to the above-mentioned related art, a tubular support member is provided in the inside of the distal hard portion of the insertion portion and a tubular support member is provided in the inside of the distal hard portion. The ultrasonic transducer array is secured in such a manner that the ultrasonic transducer array is fitted on the support member and the ultrasonic transducer array are clamped on the distal and proximal opposite ends thereof. Stopper means for the ultrasonic transducer array is provided on one of distal and proximal clamping members. The ultrasonic transducer array is fixed to the inside support section and to the distal and proximal clamping members by an adhesive so that the airtightness of joining sections can be ensured. Accordingly adhesion sections on the opposite ends of the ultrasonic transducer array are exposed to the outside, and the adhesive in this exposed section is degraded by heat treatment during sterilization of the insertion portion or by immersion of the insertion portion into an antiseptic solution. This degradation causes problems such as lowering of seal functions of the adhesion sections.
In this construction, the acoustic lens is a member which constitutes the external circumferential section of the ultrasonic transducer array, and if a material which is higher in sonic speed than living bodies is used as the material of the acoustic lens, the acoustic lens is constructed as a concave lens, while if a material which is lower in sonic speed than living bodies is used as the material of the acoustic lens, the acoustic lens is constructed as a convex lens. The acoustic lens is desirably constructed from a convex lens in terms of adhesiveness to the internal walls of body cavities. The sonic speed of silicone rubber is about 1000 m/sec, and the sonic speed of living bodies is 1530 m/sec. Accordingly, silicone rubber can be used as the material of the acoustic lens.
The invention has been made in view of the above-mentioned problems, and an object of the invention is to reduce the number of joining sections to be exposed from the outside surface of a section in which an ultrasonic transducer array is fitted.
The insertion portion of the ultrasonic endoscope is inserted into the body of a subject for the purposes of various examinations and treatments, so that the diameter of the insertion portion need be made as thin as possible. If the accuracy of examination by the ultrasonic observation means is to be increased, it is necessary to increase the size of each of the ultrasonic transducers so as to increase the output power thereof. Accordingly, not only the thickness of each of the ultrasonic transducers increases, but also the thickness of the backing layer must be increased. The endoscopic mechanism is inserted in the tunnel-shaped path formed in the inside of the backing layer.
The endoscopic mechanism needs at least an illumination section and an observation section because the endoscopic mechanism is used to optically observe body cavities. There is also a case where other members such as a treatment equipment insertion channel and a cleaning-fluid supply tube for an observation window are provided in the endoscopic mechanism. In the observation section in particular, there is a case where an objective lens and a solid-state image pickup device as well as, if necessary, various filters and a prism for bending an optical path are provided. The treatment equipment insertion channel is constructed to allow forceps and other treatment equipments to be inserted through, and is desirably made of a thick tube in order to allow insertion of large-sized treatment equipments.
As described above, the ultrasonic endoscope has the problem that if any of the functions of the ultrasonic observation means or the endoscopic mechanism is to be improved, the insertion portion must be made thick as needed. The inside diameter of the backing layer in particular has an extremely large influence on the fitting of the endoscopic mechanism. An object of the invention is to make it possible to ensure a wide fitting space for the endoscopic mechanism by making as wide as possible the cross section of the tunnel-shaped path formed by the backing layer.